Microsomal alcohol oxygenase: Purification and characterization of a cytochrome P450 responsible for oxidation of 7-hydroxy-Delta(8)-tetrahydrocannabinol to 7-oxo-Delta(8)-tetrahydrocannabinol in guinea pig liver

摘要

Guinea pig hepatic enzyme, microsomal alcohol oxygenase, was able to oxidize both 7 alpha- and 7 beta-hydroxy-Delta(8)-tetrahydrocannabinol (7 alpha- and 7 beta-hydroxy-Delta(8)-THC) to 7-oxo-Delta(8)-THC. A cytochrome P450, named P450GPF-B, which mediates this oxidative metabolism was purified from hepatic microsomes of untreated female guinea pigs. The purified enzyme showed a single protein band of molecular mass 50,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The NH2-terminal amino acid sequence of P450GPF-B is highly homologous with those of several cytochrome P450s belonging to the CYP3A subfamily, O-18 derived from atmospheric oxygen was incorporated into 31 and 6%, respectively, of 7-oxo-Delta(8)-THC formed from 7 alpha- and 7 beta-hydroxy-Delta(8)-THC when the substrates were incubated with P450GPF-B under O-18(2). The antibody against P450GPF-B significantly suppressed the oxidative activities of 7 alpha- and 7 beta- hydroxy-Delta(8)-THC to 7-oxo-Delta(8)-THC in hepatic microsomes of guinea pig, These results indicate that P450GPF-B is a major enzyme responsible for the hepatic microsomal alcohol oxygenase activities in the guinea pig. (C) 1997 Academic Press.